Have you ever heard stories about malicious USB thumb drives frying laptops and thought they were far fetched? An electronics engineer heard them too, and then set out to create a prototype.

The “USB Killer” device was created by a do-it-yourself hardware enthusiast who described his project, complete with pictures and technical details, on a Russian blogging platform in February. An English-language version was posted on a different site earlier this week.

The malicious USB thumb drive uses an inverting DC-to-DC converter to draw power from the computer’s USB port in order to charge a capacitor bank to -110 Volts (negative voltage). The power is then sent back into the USB interface via a transistor and the process is repeated in a loop.

“The combination of high voltage and high current is enough to defeat the small TVS diodes on the bus lines and successfully fry some sensitive components—and often the CPU,” hardware hacking site Hackaday reports. “USB is typically integrated with the CPU in most modern laptops, which makes this attack very effective.”

The creator of USB Killer, who uses the online alias Dark Purple, claims to work for a company that manufactures electronics and said that he ordered the custom printed circuit board and other components he needed for the project from China.

He allegedly got the idea to create the destructive device after hearing a story about a guy who stole a USB flash drive from someone’s backpack on the subway and it fried his laptop when he plugged it in.

Security researchers have long warned about the security risks of inserting other people’s USB drives into your PC, and even those from people you do trust. However if the threat of malware infections doesn’t scare you enough to stop doing this, the possibility of electrical damage might.